The information within a QR code can vary--it can be a phone number, a website link, a link to play a video, a link to map directions, and more.
What do I need?
To decipher the code you need a web-enabled phone with a camera, and a decoding application called a barcode scanner. These scanner apps are freely available for a variety of mobile devices--you can pick a scanner app from this list: http://bit.ly/fJGqz9
How do I scan this QR code?
After downloading and launching a code scanner application, simply point your device's camera at the QR code and the app will reveal the information in your device by linking you there, usually using your device's web browser. For example, scanning the QR code above will take you to the library's mobile website.